An essential part of normal pregnancy is cervical remodeling, the process by which the collagen microstructure disorganizes and the cervix softens throughout pregnancy to allow eventual delivery of a fetus. Timing is everything; errors result in preterm or post-dates birth, both of which are costly and morbid. Remark- ably, there are currently no tools to objectively quantify these changes, leaving clinicians without a means to precisely determine risk or even a language to accurately communicate the status of a patient's cervix. The primary objective of this proposed effort is to further develop and test technology to objectively describe and quantify cervical microstructural collagen arrangement and softening. A secondary objective is to establish a nonhuman primate (NHP) model for the study of cervical remodeling in pregnancy. Our preliminary studies suggest that two quantitative ultrasound techniques can accurately assess changes in microstructural organization and softness: quantitative ultrasound with beamsteering (QUS) and acoustic radiation force impulse (ARFI). Within this proposed effort we will use these techniques to study the microstructural changes that the cervix undergoes during normal pregnancy in NHPs. There are two branches: the first involves hysterectomy specimens and the second live NHPs. For the former, we will study normal specimens from animals being euthanized for unrelated research projects. Half of the group will undergo cervical ripening with a drug used clinically to ripen the cervix prior to induction of labor, and half will receive no treatment. Quantitative ultrasound measurements of acoustic scattering properties (to describe collagen structure) and tissue softness will be compared in these two groups, and nonlinear optical microscopy (for imaging collagen) will be used to corroborate the ultrasound findings. (This comparison parallels that underway in similar studies of human subject hysterectomy specimens.) The other branch will be a serial study of quantitative ultrasound parameters at several time points throughout normal menstruation (to establish underlying biological variability), and then normal pregnancy (to describe collagen reorganization and cervical softening in pregnancy). A successful NHP model of cervical ripening in pregnancy would add significantly to the body of knowledge about the cervix and accelerate transition to in vivo human studies. Ultimately, a comprehensive understanding of cervical change in pregnancy could allow (a) selection of appropriate candidates for post-dates induction of labor, (b) prediction of patients at greatest risk for preterm delivery, (c) monitorin of treatments for preterm birth or failed post-dates ripening, and most importantly, (d) development of innovative therapeutic strategies for both preterm and post-dates birth via targeted investigation of associated molecular events based on thorough understanding of specific microstructural changes that lead to abnormal cervical remodeling.